<!DOCTYPE html>
<html>
    <head>
        <style type="text/css">
            body {
                margin: 0;
            }
            .bg {
                background-color: green;
                width: 400px;
                height: 400px;
            }
            .fg {
                background-color: yellow;
                position: absolute;
                width: 100px;
                height: 100px;
                left: 150px;
                top: 150px;
            }
        </style>
    </head>
    <body>
        <div class="bg"></div>
        <div class="fg"></div>
    </body>
</html>
